7.2 Cluster Support

7.2.1 Clustering in NetWare 6.0

In NetWare 6.0, you deployed older versions of DNS servers
in a clustered environment and configured a DNS server on each of
the nodes in the preferred node list corresponding to the resource.
If the current node failed, the DNS server migrated from the current
node to another node, depending on the sequence of nodes in the
preferred node list. The number of DNS server objects equaled to
the number of nodes in the preferred node list.

Although older versions of DNS servers supported clustering,
it was limited to starting a DNS server and had its own identity.
This server identity was different from the DNS server running on
the next node.

For example, consider the following scenario:

The preferred node list has Node 1,
Node 2, and a designated primary DNS server (DNS server object 1)
running on Node 1. This DNS server is supposed to handle the dynamic
updates received from the DHCP server.

An outage happens on Node 1 and the DNS server migrates
to Node 2.

Node 2 uses another DNS server (DNS server object
2), which is not a designated primary DNS server. It cannot handle
the dynamic updates, so the identity of the DNS server is lost during
a node outage.

7.2.2 Clustering in NetWare 6.5

In a clustered environment, the new DNS server, by default,
supports the functionality provided by the older versions of DNS
server. In addition, you can configure a new DNS server to maintain
its identity after a node outage. In such case, only one DNS server
is required per failover path (preferred node list) instead of one
DNS server per node, as was the case with the older versions of DNS
server.

7.2.3 Creating a Cluster-Enabled DNS Server

Consider the following scenario for an existing DNS server:

The old DNS server is running in a
cluster with one DNS server per node in the preferred node list.
For any set of zones, only one of these can be a designated DNS
server and the rest are passive DNS servers.

A second DNS server running without a cluster.

To migrate this setup, you must consider the following points
if you want the DNS server to take advantage of the new functionality
and maintain its identity after an outage:

All NCP™ servers in the preferred
node list should be upgraded to NetWare 6.5.

DNS server objects should not be created on an NCP
server that is part of any existing preferred node list.

Before moving any server, the DNS server should
be brought down.

Any node that is considered as a potential candidate
to host DNS Services should be part of the only preferred node list.

You must also decide the following:

Identify the DNS server object that
has to be retained from the DNS servers corresponding to all nodes
in the preferred node list. All other DNS server objects must be
removed.

If you want to retain all DNS server objects, create
a separate failover path for every DNS server object.

7.2.4 Configuring a DNS Server in a Clustered
Environment

Make sure that
the server has been upgraded to NetWare 6.5.

Run nwdeploy.exe from
the root of the NetWare 6.5 Operating System CD to upgrade the cluster
software.

Launch ConsoleOne.

Create a Virtual NCP server by making
a shared volume as cluster-enabled.

In order to make an existing non-cluster-enabled DNS server
support clustering, use the move DNS server feature as follows:

Upgrade the
server to NetWare 6.5.

Launch one of the DNS/DHCP management
utilities.

Identify the NCP server and the corresponding
DNS server object that should be retained.

Make sure that the DNS Services is not running on this NCP
server.

Identify the Virtual NCP server where
DNS Services will be based.

Unlike old DNS servers that were cluster-enabled as a cluster
resource, this should be cluster-enabled as a volume resource corresponding
to the shared volume. Do this with the ConsoleOne snap-ins for Clustering
Services.

Make sure that none of the nodes in the
preferred node list has an associated DNS server (except the NCP
server selected in Step 4 if it
is part of the preferred node list).

Do this by deleting all other DNS servers in the preferred
node list or moving them out of the preferred node list.

Use one of the DNS/DHCP management
utilities to move the DNS server from the NCP server identified
in Step 3 to the Virtual
NCP server identified in Step 4.